Re: [U-Boot] [PATCH 3/5] fdt: Allow stacked overlays phandle references

On 30 June 2017 at 10:23, Pantelis Antoniou pantelis.antoniou@konsulko.com wrote:

This patch enables an overlay to refer to a previous overlay's labels by performing a merge of symbol information at application time.

In a nutshell it allows an overlay to refer to a symbol that a previous overlay has defined. It requires both the base and all the overlays to be compiled with the -@ command line switch so that symbol information is included.

base.dts

    /dts-v1/;
    / {
            foo: foonode {
                    foo-property;
            };
    };

    $ dtc -@ -I dts -O dtb -o base.dtb base.dts

bar.dts

    /dts-v1/;
    /plugin/;
    / {
            fragment@1 {
                    target = <&foo>;
                    __overlay__ {
                            overlay-1-property;
                            bar: barnode {
                                    bar-property;
                            };
                    };
            };
    };

    $ dtc -@ -I dts -O dtb -o bar.dtb bar.dts

baz.dts

    /dts-v1/;
    /plugin/;
    / {
            fragment@1 {
                    target = <&bar>;
                    __overlay__ {
                            overlay-2-property;
                            baz: baznode {
                                    baz-property;
                            };
                    };
            };
    };

    $ dtc -@ -I dts -O dtb -o baz.dtb baz.dts

Applying the overlays:

    $ fdtoverlay -i base.dtb -o target.dtb bar.dtb baz.dtb

Dumping:

    $ fdtdump target.dtb
    / {
        foonode {
            overlay-1-property;
            foo-property;
            linux,phandle = <0x00000001>;
            phandle = <0x00000001>;
            barnode {
                overlay-2-property;
                phandle = <0x00000002>;
                linux,phandle = <0x00000002>;
                bar-property;
                baznode {
                    phandle = <0x00000003>;
                    linux,phandle = <0x00000003>;
                    baz-property;
                };
            };
        };
        __symbols__ {
            baz = "/foonode/barnode/baznode";
            bar = "/foonode/barnode";
            foo = "/foonode";
        };
    };

Signed-off-by: Pantelis Antoniou pantelis.antoniou@konsulko.com

lib/libfdt/fdt_overlay.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 147 insertions(+), 1 deletion(-)

Reviewed-by: Simon Glass sjg@chromium.org

I suppose that the upstream version has tests?

Does it make sense to implement this in the live tree instead, or do you need to modify the DT before relocation?

- Simon